1. Field of the Invention
The present invention relates to an inkjet recording apparatus and an inkjet recording method which use a pigment ink. More specifically, the present invention relates to the inkjet recording apparatus and the inkjet recording method which can bring about a high quality image that is excellent in ink absorbing property and fixing property and has good color tone, can bring about an image that is excellent in image rigidity such as water-proof and light-proof, is excellent in storage stability and is excellent in ejection stability free from head's clogging in the printing.
2. Description of the Related Art
From its advantages such as low noise, low running cost and the like, an inkjet recording apparatus is remarkably pervaded, and a color printer capable of printing color image on plain paper in addition to an inkjet recording medium is more and more placed on the market. It is, however, very difficult to meet all required properties including color reproducibility of an image, durability, light resistance, image dryness, character feathering, color boundary bleeding (for short, color bleeding), both-side printing property, ejection stability, and the like. With this, the ink used is selected based on a preferential property for a specific application. Especially, meeting the above required properties are difficult for the printer for high-speed plain paper printing.
Generally, with its principle component of water, the ink for the inkjet printing contains a coloring agent, and further contains a wetting agent such as glycerin and the like for clogging prevention. As the coloring agent, dye is used in view of its excellent coloring property and stability. An image obtained by using a dye ink does not have good light resistance, waterproof, and the like. The waterproof is improved to a certain extent by improvement of inkjet record paper having an ink absorbing layer, which improvement does not, however, apply sufficiently to the plain paper.
Recently, for solving the above problems, a pigment ink using as coloring agent an organic pigment, carbon black and the like in place of the dye is taken into account. The pigment is insoluble in water. Thereby, the pigment can be used as an aqueous ink in which the pigment is mixed and dispersed with a dispersing agent for stable dispersion in water. Use of the pigment can bring about waterproof and light resistance, but cannot meet other properties at the same time. Especially, the high-speed printing of the plain paper cannot obtain high image density and high coloring property, failing to sufficiently meet the character feathering, the color bleeding, the both-side printing property and the like.
In the inkjet printing, a stable ejection of an ink droplet from a thin nozzle of an inkjet recording head is needed. For meeting the above, it is necessary that dryness of an orifice of the inkjet recording head does not cause solidification and the like of the ink. Use of a dispersing agent-contained ink for the inkjet printing may sometimes cause clogging or ink's ejection failure which may be attributable to a resin and the like (of the dispersing agent) that is not dissolved again after adhering to the orifice and the like. Especially, a long-time stoppage of the printing is likely to cause the clogging of the nozzle and the like, moreover, the long-time stoppage may cause ink's accumulation (the ink with increased viscosity) in a nozzle cap or in a maintenance mechanism such as intake-tube and the like, thus losing function of the maintenance mechanism. A temporary stoppage of printing, or a temporary stoppage of using a nozzle that corresponds to a blanked document or a blanked image may cause a printing failure and the like which may be attributable to disoriented direction of injection of ink droplet (intermittent ejection failure). The above problems occurred so often. An aqueous pigment ink containing the dispersing agent is viscous and causes a resistance in a path to a nozzle's head end in the long-time continuous ejection and a high-speed printing, thus making the ejection unstable and making it difficult to achieve a smooth printing.
For solving the above problems, the following inks are to be proposed.
Resin Dispersion Pigment Ink
For solving the above problems, Japanese Patent Application Laid-Open (JP-A) No. 2000-212486 discloses an ink having specific agents and property such as pigment, pigment density, water-soluble dispersing agent, and penetrating agent; an ink containing polyhydric alcohol alkylether derivatives; and an ink set thereof. The ink disclosed in JP-A No. 2000-212486 has a super permeability, and thereby has a sufficient dryness even at a high-sped printing and has a secured ejection stability. The ink disclosed in JP-A No. 2000-212486 is, however, inferior to a dye ink in terms of image density, color reproducibility and the like when the plain paper is used. Although more improved in character feathering, color bleeding and both-side printing property than a conventional inkjet record image, a record image disclosed in JP-A No. 2000-212486 is inferior to a record image of an electrophotographic method and the like used for plain paper printing on the market, thereby is in need of more improvement.
Ink Containing Coloring Agent-Encapsulated Resin Dispersion
For improving durability of the image, an ink is disclosed which contains a coloring agent-encapsulated resin dispersion which encapsulates a coloring agent in an insoluble-and-dispersing resin. However, the above ink does not obtain a sufficient image density when a carbon black is used as the coloring agent. A color organic pigment used as the coloring agent for a conventional ink is inferior to a dye ink in terms of image density, color reproducibility and the like on the plain paper. An ink set of the above coloring agent-encapsulated resin dispersion which set combines a black ink with a color ink cannot bring about a sufficient color boundary bleeding between black and yellow.
Self-Dispersion Pigment Ink
Other dispersing methods include a self-dispersion pigment ink which is capable of making a stable dispersion without a dispersing agent. In terms of a black pigment ink, JP-A No. 5-186704 and JP-A No. 8-3498 disclose so-called a self-dispersion carbon black which is capable of making a stable dispersion without a dispersing agent by introducing a hydrophilic group to a surface of carbon. Moreover, in terms of a color pigment ink, JP-A No. 2000-513396 discloses a color pigment which is capable of making a stable dispersion without a dispersing agent.
Combining the above self-dispersion pigment inks is low in terms of chroma of a color image on plain paper, and deteriorated in terms of friction resistance on a special recording medium such as gloss paper.
Alternatively, JP-A No. 10-140064 discloses an ink set comprising a black ink and a color ink in which a black ink having a self-dispersion carbon black and a color ink containing a coloring material whose polarity is opposite to that of a coloring material of the black ink. Furthermore, JP-A No. 2000-191972 discloses an ink set having coloring agent-encapsulated resin dispersion inks having different ionicities. A printed matter printed with the above ink sets are improved in terms of color bleeding, however, still failing to meet other properties of the plain paper.
On the other hand, efforts for improving fitness to the pigment ink have been made with a coat paper type inkjet recording medium which is provided with a coat layer on a base material. JP-A No. 11-342669 discloses the one having an ink accepting layer mainly composed of water-soluble resin. In JP-A No. 11-342669, an inkjet recording body contains hydroxy propyl methyl cellulose, moreover the ink accepting layer contains a single polymer resin (N-vinyl pyrrolidone) or a copolymer resin (N-vinyl pyrrolidone and other polymeric monomer). JP-A No. 2000-108508 discloses an inkjet record sheet containing methoxyl group-contained water-soluble cellulose derivative and water-soluble cationic resin. JP-A No. 10-329405 discloses an inkjet record sheet which contains hydrophilic high molecular resin and a specific anionic fluorine surfactant.
As those having the ink accepting layer mainly composed of an inorganic pigment and binder resin, JP-A No. 10-119417 discloses an inkjet record sheet provided with i) a base material sheet, ii) an ink permeation layer (mainly composed of inorganic filler) disposed on the base material sheet, and iii) an ink swelling layer mainly composed of water-soluble resin. JP-A No. 10-329417 discloses an inkjet recording film has a recording layer which is a sequential lamination of (A) an ink accepting layer containing water-soluble resin, coarse face forming agent, and cross-linking agent, and (B) a layer containing dot-shape regulating agent. In the above inkjet recording film, at least two types of synthetic silicas having different oil-absorbing amount are used as the coarse face forming agent. Varying the amount of use of these may adjust the number of samplings of the recording layer in a range of 20 to 100 and adjust an ink fixing period less than 5 minutes. JP-A No. 11-99739 discloses an inkjet record sheet having a first ink accepting layer and a second ink accepting layer, in which the first ink accepting layer contains a resin component which is dissolved in or swelled with a coating solution for the second ink accepting layer. The second ink accepting layer has pigment content more than that of the first ink accepting layer. JP-A No. 11-245502 discloses an inkjet coating agent which contains a hydrophilic polyurethane and a silica mixture, where the hydrophilic polyurethane is contained in a range of 15% by weight to 90% by weight relative to an entire coating agent, while the silica mixture (containing i. a silica having an average particle diameter 6 μm to 9 μm is 10% by weight to 30% by weight, ii. a light diffusion silica having an average particle diameter 10 μm to 15 μm is 15% by weight to 40% by weight, and iii. a porous silica having an average particle diameter 10 μm to 22 μm is 15% by weight to 40% by weight) is contained (solid content) in a range of 10% by weight to 80% relative to the entire coating agent.
JP-A No. 11-291619 discloses an inkjet recording film which is a sequential lamination of an adhesive layer and an ink accepting layer, where the adhesive layer has main components including (A) a binder, (B) a coating film forming assistant, and (C) a cross-linking agent, and the ink accepting layer has main components including a binder having the same component as that of (A), (D) coarse face forming agent, a cross-linking agent having the same component as that of (C), and (E) catalyst, with the weight ratio of the binder to the coarse face forming agent 2:3 or 1:3. JP-A No. 11-301093 discloses an inkjet record material having an ink solvent transmitting layer which transmits solvent on to an ink accepting layer but not transmit pigment. JP-A No. 2000-1043 discloses an aqueous ink record material which is made from i) polyacetal resin, urea-glyoxal-acryl amide polycondensation product and epoxy compound, and resin composition composed of fine particle. JP-A No. 2000-79752 discloses an inkjet recording body containing silica and the like, and a cationic resin having cationic strength 1.5 m equivalent/g to 6 equivalent/g.
JP-A No. 2000-79752 and JP-A No. 2000-79754 disclose a record sheet which is partly deletable and which bears an inkjet printing pattern by means of a pigment ink which is incompatible with an ink accepting layer. JP-A No. 2000-127610 discloses an inkjet record sheet made from a porous starch particle and a binder resin, where an inorganic or organic particle is embedded into the porous starch particle. JP-A No. 2000-190622 discloses an inkjet record material formed of an ink accepting layer which contains an inorganic pigment, a water-soluble resin, and a metal salt (which has ion valence of 2 or more). JP-A No. 2000-238420 discloses an inkjet record sheet, where a pigment relative to a binder agent is 100 weight part relative to a range of 10 weight part 50 to weight part, a recording layer has main components including i) a synthetic silica (as pigment) having average particle diameter 3 μm to 15 μm and ii) a polyvinyl alcohol having saponification 96 mol % or more (binder agent), and quaternary ammonium salt polymer 1 weight part to 40 weight part relative to the pigment 100 weight part, and hardener 20 weight part to 100 weight part relative to the binder agent 100 weight part are contained.
JP-A No. 2000-247014 discloses an aqueous ink record material having, as main component, polyvinyl acetal resin which is obtained by acetalizing polyvinyl alcohol using aromatic aldehyde. In the polyvinyl acetal resin, a particle composed of at least one selected from the group consisting of water-soluble acrylic resin, water-soluble epoxy compound, silic acid, silica, kaolin, clay, alumina, calcium carbonate, zeolite, titanium oxide, talc, and spherical high polymer. JP-A No. 2000-318298 discloses an inkjet record sheet which has a lower layer (containing resin film, amorphous synthetic silica and water-insoluble resin), and an upper layer (containing amorphous synthetic silica, water-insoluble resin and silanol-modified polyvinyl alcohol), and which has smoothness 5 seconds to 40 seconds.
Moreover, in terms of aluminum oxide accepting layer, JP-A No. 2000-37945 discloses an inkjet record sheet where an ink accepting layer is a fixed layer fixed by a binder which has, as main components, i) aluminum oxide fine particles (two different particle diameters) and ii) saponified polyvinyl alcohol (saponification 80 mol % to 95 mol %). JP-A No. 11-198520 discloses an inkjet record material which is a sequential lamination of aluminum oxide layer (γ-type or δ-type), and a high molecular-contained layer (water-soluble or water-swelled).
Any of the above publications fail to sufficiently meet the inkjet's properties such as ink absorption, image density, beading, fixing property (friction resistance), and the like.